The Open Software License is a free software license. It is incompatible with the GNU GPL in several ways.
Recent versions of the Open Software License have a term which requires distributors to try to obtain explicit assent to the license. This means that distributing OSL software on ordinary FTP sites, sending patches to ordinary mailing lists, or storing the software in an ordinary version control system, is arguably a violation of the license and would subject you to possible termination of the license. Thus, the Open Software License makes it very difficult to develop software using the ordinary tools of free software development. For this reason, and because it is incompatible with the GPL, we recommend that no version of the OSL be used for any software.
We urge you not to use the Open Software License for software you write. However, there is no reason to avoid running programs that have been released under this license.
The reason that OSL 3.0 is incompatible has nothing to do with this. It is because OSL 3.0 requires derivative works to be under OSL that the two licensesâand MPL, and CDDL, and lots of others are incompatible with GPL as well. It is for the same reason that GPLv2 is incompatible with GPLv3.
This comment (above) may also reflect a fundamental misunderstanding of OSL 3.0 and of the GPL licenses. GPL-licensed software can link to OSL 3.0-licensed software without the OSL causing any license problem. OSL 3.0-licensed software can link to GPL-licensed software without any license problem. The OSL 3.0 license doesnât affect independently written GPL-licensed software in any way, no matter how it links.
The AGPL license (Affero GPL 3) is not OSI approved. The reason we prefer OSL 3.0 is because it is an OSI approved license.
Hope this helps resolve the confusion.